Quantification of rat supraglottic laryngeal sensation threshold

Area of Science:

• Otorhinolaryngology
• Anesthesiology
• Animal Models

Background:

• Laryngeal adductor response (LAR) to air puff is a validated method for assessing human laryngeal sensory disorders.
• Adapting this method for small animal models like rodents presents significant challenges.
• Establishing reliable methods for rodent laryngeal sensory evaluation is crucial for preclinical research.

Purpose of the Study:

• To evaluate sensation thresholds (ST) to air puff stimulation in rats using binocular microlaryngoscopy.
• To determine sensory thresholds at specific laryngeal target locations (epiglottis, arytenoid, piriform sinus).
• To identify the optimal depth of anesthesia for accurate LAR assessment in rats.

Main Methods:

• Rats were anesthetized with ketamine/xylazine, with anesthesia depth monitored via glottic closure and corneal reflexes.
• Air puffs of varying pressures were applied to the epiglottis, arytenoid, and piriform sinus under direct microlaryngoscopic visualization.
• Sensation thresholds were determined, and the effect of topical lidocaine on LAR was assessed.

Main Results:

• Mean STs were recorded at the epiglottis (39 ± 9.7 mm Hg) and arytenoid (48.8 ± 10.5 mm Hg); thresholds were undetectable at the piriform sinus.
• Repeated trials confirmed consistent results, and lidocaine effectively abolished the LAR.
• Accurate LAR induction and differentiation from spontaneous glottic closure were challenging at certain anesthesia depths.

Conclusions:

• Air pulse stimulation is a simple, reliable, and effective method for determining laryngopharyngeal STs in rats.
• This technique provides an efficient and affordable approach for experimental studies on laryngeal sensory disorders.
• The study successfully adapted a human clinical method for use in a rodent model, facilitating further research.